Research

Gravitational Waves

The research activity of our group is mainly focused around gravitational waves. We are part of the LIGO Scientific Collaboration and the LISA Consortium.

In general relativity spacetime is a dynamic and elastic entity both influencing and influenced by the distribution of mass and energy that it contains. As a consequence, the accelerated motion of mass and energy can generate ripples in the fabric of spacetime propagating at the speed of light called gravitational waves.

On September 14, 2015, LIGO (Laser Interferometer Gravitational-Wave Observatory) detected for the first time gravitational waves emitted by two colliding black holes and inaugurated the era of gravitational wave astronomy.

Gravitational waves encode unique information about the source that has generated them. Searching for and analyzing gravitational wave signals leads to a better understanding of gravitational phenomena and has an impact on astrophysics as well as fundamental physics and cosmology.

Some of our main activities include:

  • Detection:
    We are involved in the development of an unmodeled search for gravitational wave transients in the network of ground based detectors. The advantage of this method is that it does not rely on waveform models of potential gravitational wave sources, therefore it can possibly detect sources that are either currently unknown or poorly modeled.
  • Source modelling:
    We have expertise in modelling gravitational waves emitted by binary systems of compact objects, such as black holes or neutron stars. In particular, we model the signals from binaries with eccentric or precessing orbits. These models are used both in the detection of the gravitational waves and in determining their properties. Since these models are based on the theoretical predictions of the waveforms made by General Relativity, they can also be compared with detected signals to see if there is any evidence for deviations from General Relativity.
  • Tests of General Relativity:
    Gravitational waves probe general relativity in the strong field regimes which are currently out of reach for ``most experiments". We are involved in testing the consistency of the detected gravitational wave signal as predicted by general relativity. In particular we have been involved in designing a pipeline which tests the quadrupolar nature of gravitational wave signals. Also we are interested in studying the nature of the compact objects detected, which has the potential to probe quantum regimes of gravity.

Tests of General Relativity with Atomic Clocks

We are part of the ACES (Atomic Clock Ensemble in Space) project led by the European Space Agency which will place ultra-stable atomic clocks on the International Space Station. The ACES performances will be used to conduct a suit of fundamental physics experiments to test Einstein's theory of general relativity with improved accuracy. According to Einstein's theory, identical clocks placed at different positions in stationary gravitational fields experience a frequency shift that, in the frame of the PPN (Parameterized Post-Newtonian) approximation, depends directly on the Newtonian potential at the clock position. The comparison between the ACES onboard clocks and ground-based atomic clocks will measure the frequency variation due to the gravitational red-shift with a huge improvement on previous experiments.